The present invention relates to a method for forming a groove in an end face of a rod of metal (e.g. iron).
When a groove 54 is formed in an end face 52 of a rod 50 as shown in FIG. 4A, the groove 54 is, in the prior art, formed by, for example, a cutting operation with a milling machine, or through plastic working with punch and die.
In such a conventional milling method, however, a long processing time is required and only a low yield is achieved. On the other hand, in the latter punch and die conventional method, as shown in FIG. 5, the rod 50 is inserted in a bore 57 of a die 56 and formed by a pair of punches 58 and 60 which are similarly inserted in the bore 57. Since the forming is performed in such an enclosed space, the life of a metal mold 56 is shortened, the frequency of replacement of the broken metal mold is increased and, thus, the working efficiency is low.